The phrase "intercalary year" is correct and usable in written English.
It typically refers to an additional day or month in a calendar year, which is added to bring the calendar into agreement with the solar year. For example, an intercalary year was added to the ancient Egyptian calendar every four years to make the calendar more closely match the length of the solar year.
Religious ceremonies were organized according to two lunar calendars that had months of 29 or 30 days, with extra, intercalary months every three years or so.
Most ancient societies readjusted their calendars by adding a thirteenth, "intercalary" month every three years or so, although methods of calculating the length of these months, and when they should be added, were never precise.
It allows for a periodic leap year and an intercalary month.
The 13 inlays mentioned above represent the 12 months of the year and the intercalary month added every few years to synchronize the lunar calendar with the solar calendar.
It was not until well into Roman times that an intercalary day once every four years was instituted to retain coincidence.
Having mastered the Bhagavad Gita and Ramcharitmanas at a very young age, Giridhar started visiting the Katha programmes held near his village once every three years in the intercalary month of Purushottama.
Each year had five or six intercalary days to make up the total of 365 or 366 days.
Under the Republican calendar, when the intercalary month Mercedonius was added to a year, it was placed after February 23 or February 24, and some ancient writers believed that the Terminalia on February 23 had once been the end of the year.
Intercalary months have been inserted to keep the calendar year in step with the solar year of about 365 days.
Starting about 380 bc, however, fixed rules regarding intercalations were established, providing for the distribution of seven intercalary months at designated intervals over 19-year periods.
It is a solar calendar consisting of 19 months of 19 days each, with 4 or 5 "intercalary" days filling out the remainder of the solar year.
